Deposit-free burner

ABSTRACT

In order to improve a burner for generating hot gas comprising a burner pipe, a nozzle arranged in the burner pipe and having an outlet in its front face, a fuel jet exiting through the outlet, a shield arranged near the nozzle for subdividing the burner pipe into a precombustion chamber located upstream and accommodating the nozzle and a combustion chamber located downstream, a central passage arranged in the shield for the fuel jet exiting from the outlet and a plurality of openings surrounding the passage in the shield, combustion air passing through the openings from the precombustion chamber into the combustion chamber such that deposits are no longer formed therein, it is suggested that an air gap is provided between the shield and the nozzle, combustion air passing through the air gap from the precombustion chamber through the passage into the combustion chamber, and that a rim of the passage is provided with a flow disruption edge for the combustion air passing through the air gap.

The invention relates to a burner for generating hot gas comprising aburner pipe, a nozzle arranged in the burner pipe and having an outletin its front face, a fuel jet exiting through the outlet, a shieldarranged near the nozzle for subdividing the burner pipe into aprecombustion chamber located upstream and accommodating the nozzle anda combustion chamber located downstream, a central passage arranged inthe shield for the fuel jet exiting from the outlet and a plurality ofopenings surrounding the passage in the shield, combustion air passingthrough the openings from the precombustion chamber into the combustionchamber.

Burners of this type are known, for example, from EP-A-0 175 875.

The disadvantage of these burners is in the fact that a heat contactexists between the nozzle and the front face of the nozzle so that thenozzle is warmed up by the hot shield and, in particular, after theburner has been switched off, the oil cracks outside the nozzle or alsoin the interior of the nozzle and forms clogging soot deposits and/oroil carbon deposits on the nozzle ducts or on the outlet of the nozzleso that the burner becomes inoperable.

Thus, the object of the invention is to improve a burner of the generictype such that deposits are no longer formed therein.

This object is accomplished in accordance with the invention, in aburner of the type described at the outset, in that an air gap isprovided between the shield and the nozzle for combustion air to passthrough the air gap from the precombustion chamber through the passageand into the combustion chamber, and that a rim of the passage isprovided with a flow disruption edge for the combustion air flowingthrough the air gap.

By means of the solution according to the invention, on the one hand, athermal contact is eliminated between the heated shield and the nozzle,in particular, the front face of the nozzle and, in addition, it isensured by the flow disruption edge that the air flowing through thepassage frees the air gap, on the one hand, and the passage itself, onthe other hand, from adhering deposits.

It is particularly favourable when the passage is provided with wallsurfaces extending conically in the direction of the combustion chamber,since such a design of the wall surfaces prevents an interference of thefuel jet, particularly, of the spray cone formed by the fuel jet. Withrespect to the position of the flow disruption edge, no

further details have been given as yet. In fact, it has proven to beparticularly advantageous for the flow disruption edge to be located onthe side of the conically extending wall surfaces facing the front faceof the nozzle, so that the flow disruption edge represents the narrowestpoint of the opening.

Particularly expedient conditions result when the flow disruption edgelies in a plane which extends vertically to an axis of the nozzle.

In addition to this, the air gap and the effect of the flow disruptionedge can be optimally designed when an annular surface adjoins the flowdisruption edge on the upstream side of the shield in radial directionto the passage, i.e. in particular, to the axis of the nozzle.

It is particularly advantageous when the annular surface is plane andextends essentially at right angles to axis of the nozzle.

This is realized in a particularly easy, constructive manner when theplane annular surface lies essentially in a plane which is defined bythe upstream surface of the shield.

The air gap is realized in a particularly easy manner in one of theembodiments described above, when a front side of the front face of thenozzle is arranged upstream at a distance from the flow disruption edgein axial direction of the nozzle. In this case, it is ensured that evena slight leakage of oil from the front face of the nozzle will not leadto a conglutination in the area of the flow disruption edge.

Moreover, it is a further advantage when the front face of the nozzle isarranged upstream at a distance from the annular surface in axialdirection to the nozzle, so that the air gap is formed between theannular surface and the front face of the nozzle.

With respect to the dimensioning of the central passage, no details havebeen specified as yet. Thus, it has proven to be favourable, within thescope of the invention, when the central passage has in the area of theflow disruption edge a diameter which is approximately the same size asthe diameter of the front face of the nozzle.

A particularly expedient dimensioning of the inventive solution resultswhen the diameter of the flow disruption edge is smaller than or thesame as the diameter of the front face of the nozzle.

Further features and advantages of the invention are the subject matterof the following description as well as the illustrated representationof an embodiment.

In the drawings:

FIG. 1 shows a longitudinal section through the embodiment and

FIG. 2 shows a section along line 2--2 in FIG. 1.

The invention concerns the most varied oil burners and is discussed inthe following using a so-called blue burner as example, i.e., a burnerin which oil is burnt completely with a blue flame. The invention is,however, not limited to such blue burners, for example, the advantageaccording to the invention can also be achieved with the describedconstructive measures using yellow burners.

The burner represented in FIGS. 1 and 2 comprises a cylindrical burnerpipe 10 which is subdivided by means of a wall, hereinafter designatedas shield 12, into a precombustion chamber 14 located upstream and acombustion chamber 16 located downstream.

In the precombustion chamber 14 a nozzle 18, which is connected with afuel supply line 20, is arranged coaxially to the burner pipe 10. Thisnozzle 18 is provided with an outlet 24 which is arranged coaxially toits axis 22 and in a front face 26 of the nozzle 18.

A fuel jet 28 exits from this outlet 24 and passes through a centralpassage 30 in the shield 12 and enters the combustion chamber 16. Thecentral passage 30 is, thereby, arranged coaxially to the axis 22 of thenozzle 18 and has conically designed edge surfaces 32 which extend froma flow disruption edge 34 up to a surface 36 of the shield locateddownstream. The flow disruption edge 34 is surrounded by a plane annularsurface 38 upstream of the conical outer surfaces, the annular surfaceextending essentially at right angles to the axis 22 and preferably liesin one plane with the surface 40 of the shield 12 located upstream.

The nozzle 18 is arranged with its front face 26 upstream at a distancefrom the annular surface 38 in the direction of the axis 22 and ispreferably aligned parallel to the plane in which the annular surface 38is located, that means, at right angles to the axis 22.

Thus, an air gap 44 results between the annular surface 38 and the frontface 26 of the nozzle, combustion air passing through this air gap tojoin the fuel jet 28 and flows together with this fuel jet through thepassage 30.

The flow disruption edge 34 forms the narrowest point of the passage 30and preferably has a diameter which is approximately equal to thediameter of the front face 26 of the nozzle or is smaller than the same.

In the solution according to the invention, the nozzle 18 is, thus,separated from the heated shield 12 by the air gap 44 and, in addition,the flow disruption edge 34 of the passage 30 leads to the fact thateven when particles are deposited in the area of the passage 30, theseare loosened when operating the burner, so that the air gap 44 does notget blocked and also the passage 30 always remains free of soot and oilcarbon deposits even during longer operation.

A mixing tube 50, preferably, adjoins the shield 12 downstream, themixing tube forming a connection via peripheral slots 52 directlyfollowing the shield 12 between its interior space 54 forming the mixingchamber and an annular space serving as recirculation chamber 56 whichconcentrically encircles the mixing tube 50.

An ignition means 60 is guided from the precombustion chamber 14 throughthe shield 12 and ends in the area of a window 62 in the mixing tube 50,so that an ignition can take place in this area.

In a similar manner, a measuring probe 64 is guided from theprecombustion chamber 14 through the shield 12 and into the combustionchamber 16.

As represented in FIG. 2, in particular, a plurality of openings 66 eachhaving a circular cross section, are arranged in a circle surroundingthe central passage 30 which form a connection between the precombustionchamber 14 and the interior space 54 surrounded by the mixing tube 50 inthe combustion chamber 16. The openings preferably lie within a surface,which results from the projection of the inside cross-sectional area ofthe mixing tube onto the shield 12. Further, the openings 66 arepreferably arranged such that the openings 66 are bevelled on the sideof the shield 12 facing the precombustion chamber 14 and preferablynarrow conically in a downstream direction.

We claim:
 1. A burner for generating hot gas comprising:a burner pipe; a shield for subdividing said burner pipe into a precombustion chamber located upstream and a combustion chamber located downstream; a nozzle in said precombustion chamber near said shield, said nozzle having a front face and an outlet therein for fuel to jet therefrom; a passage in said shield for the flow therethrough of fuel from said nozzle outlet, said passage having an interior wall surface extending conically and divergently in the direction of the combustion chamber; a plurality of openings surrounding said passage in said shield for combustion air to pass from the precombustion chamber into the combustion chamber; a flow disruption edge in said passage in said shield; a small gap between said shield and said nozzle for an amount of air to pass therethrough into said passage in said shield with disruption by said flow disruption edge, whereby said gap and said passage are maintained free of adhering deposits of soot and oil carbon by said flow of air therethrough.
 2. A burner according to claim 1 characterized in that the flow disruption edge is located on the side of the conically extending wall surfaces facing the front face of the nozzle.
 3. A burner according to claim 1, characterized in that the flow disruption edge is in a plane extending vertically to an axis of the nozzle.
 4. A burner according to claim 1, characterized in that an annular surface adjoins the flow disruption edge on the upstream side of the shield in a radial direction to the passage, which in conjunction with said front face of said nozzle forms said gap between said shield and said nozzle.
 5. A burner according to claim 4, characterized in that the annular surface is plane and extends at right angles to the axis of the nozzle.
 6. A burner according to claim 5, characterized in that the plane annular surface lies essentially in the plane defined by the upstream surface of the shield.
 7. A burner according to claim 1, characterized in that the front face of the nozzle is arranged upstream at a distance from the flow disruption edge in an axial direction of the nozzle.
 8. A burner according to claim 7, characterized in that the front face of the nozzle is arranged upstream at a distance from the annular surface in an axial direction of the nozzle.
 9. A burner according to claim 1, characterized in that the passage has in the area of the flow disruption edge a diameter approximately the same size as the diameter of the front face of the nozzle.
 10. A burner according to claim 1, characterized in that the diameter of the flow disruption edge is smaller than or the same as the diameter of the front face of the nozzle. 